Multi-dimensional ultrasonic array interconnect

Abstract

An ultrasonic transducer array has a piezoelectric ceramic layer that is separated in a longitudinal direction into n transducer groups. Each group is separated in a transverse direction into m elements. A double-sided flex circuit has a flexible, non-conductive base layer, through which conductive vias extend and are in electrical contact with a respective element. A conductive layer on a bottom side of the flex circuit is divided into a plurality of electrodes, each of which is in electrical contact with a respective one of the elements. For each group, electrically conductive traces connect predetermined ones of the flex circuit electrodes with external driving circuitry, and are located on a top side of the flex circuit. Transducer groups with different numbers of elements are provided, some with 1.5-D operation (with element pairs stimulated via a common trace) and some with 2-D operation (with separate traces for each element). For embodiments with more than three elements per group, the flex circuit includes more than one base layer. The invention also makes it possible at most two traces located on the top side of the flex circuit for each group, measured in the longitudinal direction. In one implementation, each array group was no wider than 300 μm, each trace was at least 50 μm, and the separation between each via and the nearest trace which is not connected to it was at least 75 μm.

We claim: 
     
       1. An ultrasonic transducer array comprising: A. a piezoelectric ceramic layer separated in a longitudinal direction into n transducer groups, with each group separated in a transverse direction into m transducer elements;   B. a flex circuit that includes: 1) a flexible, electrically non-conductive base layer;   2) for each transducer element, an electrically conductive via through the base layer in electrical contact with the respective transducer element;   3) an electrically conductive layer, on a bottom side of the flex circuit, that is divided into a plurality of flex circuit electrodes, with each flex circuit electrode being in electrical contact with a respective one of the transducer elements; and   4) for each group, electrically conductive traces that are electrically connected by vias to predetermined ones of the flex circuit electrodes and to external driving circuitry, and are located on a top side of the flex circuit     in which the electrically conductive layer, and thus the flex circuit electrodes, as well as the electrically conductive traces and vias are pre-patterned onto the flexible base layer, the flex circuit thereby forming a pre-patterned, pre-aligned unit.   
     
     
       2. An ultrasonic transducer array as defined in claim 1, in which at most two traces are located on the top side of the flex circuit for each group, measured in the longitudinal direction. 
     
     
       3. An ultrasonic transducer array as defined in claim 2, in which: A. each transducer group has three elements--a center element and two outer elements; and   B. the two outer elements are electrically connected by a single trace.   
     
     
       4. An ultrasonic transducer array as defined in claim 2, in which, measured in the longitudinal direction: A. each array group is no wider than 300 μm;   B. each trace is at least 50μm; and   C. the separation between each via and the nearest trace which is not connected to it is at least 75 μm.   
     
     
       5. An ultrasonic transducer array as defined in claim 2, in which: A. each transducer group has three elements--a center element and two outer elements; and   B. each group has three traces and each element is electrically connected to and independently stimulated over a different one of the traces.   
     
     
       6. An ultrasonic transducer array as defined in claim 1, in which: A. the transducer groups each contain more than three elements;   B. the flex circuit includes a plurality of flexible, electrically non-conductive base layers;   C. the electrically conductive vias extend through all the base layers and are in electrical contact with the respective transducer element;   D. the electrically conductive traces are located on a top surface of each base layer; and   E. at most two traces are located on the top surface of any base layer for each group, measured in the longitudinal direction.   
     
     
       7. An ultrasonic transducer array as defined in claim 1, in which: A. each transducer group has five elements--a center element, two intermediate elements, and two outer elements;   B. separate traces are provided for the center element and the outer elements of each group;   C. vias are provided only for the center element and the intermediate elements;   D. the outer elements have separate traces that directly connect the flex circuit electrodes for the outer elements with the external circuitry and are located entirely off of the top surface of the base layer;   E. at most two traces are located on the top surface of the base layer for each group, measured in the longitudinal direction; and   F. each of the five elements in each group is thereby provided for independent stimulation over a respective trace.